Manufacturing method of a semiconductor device and method for creating a layout thereof

ABSTRACT

A method for manufacturing a semiconductor device of one embodiment of the present invention includes: forming an insulation layer to be processed over a substrate; forming a first sacrificial layer in a first area over the substrate, the first sacrificial layer being patterned to form in the first area a functioning wiring connected to an element; forming a second sacrificial layer in a second area over the substrate, the second sacrificial layer being patterned to form in the second area a dummy wiring; forming a third sacrificial layer at a side wall of the first sacrificial layer and forming a fourth sacrificial layer at a side wall of the second sacrificial layer, the third sacrificial layer and the fourth sacrificial layer being separated; forming a concavity by etching the insulation layer to be processed using the third sacrificial layer and the fourth sacrificial layer as a mask; and filling a conductive material in the concavity.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. Ser. No. 15/719,135, filed Sep. 28,2017, which is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. Ser. No. 15/408,562, filed Jan. 18,2017, which is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. Ser. No. 14/829,250, filed Aug. 18, 2015which is a continuation of U.S. Ser. No. 14/492,940, filed Sep. 22,2014, now U.S. Pat. No. 9,209,070, which is a continuation of U.S. Ser.No. 13/665,803, filed Oct. 31, 2012, now U.S. Pat. No. 8,865,583, whichis a continuation of U.S. Ser. No. 12/332,788, filed Dec. 11, 2008, nowU.S. Pat. No. 8,298,928, and claims the benefit of priority under 35U.S.C. § 119 from Japanese Patent Application No. 2007-320444 filed Dec.12, 2007; the entire contents of each of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention is related to a method which employs side wall processingduring the manufacture of a semiconductor device.

Description of the Related Art

Semiconductor devices are now widely used in a number of differentfields. The demands for small scale semiconductor devices, reductions inthe amount of energy consumption, improvements in reliability, andreductions in costs are increasing year by year. Particularly, in orderto achieve small scale semiconductor devices an increased level ofmanufacturing technology is being demanded as the number of elementsincluded in a semiconductor device per unit area is increasing.

A reduction in wiring width or a reduction in spaces between wirings isgiven as one method for achieving small scale semiconductor devices.However, in contemporary lithography technologies in which a patternsuch as a wiring is formed using optical lithography, there are limitsto the level of resolution due to the wavelength used. Thus, as a methodwhich overcomes the limits of this resolution for forming a pattern, theside wall processing (also called side wall transfer processing) isproposed, for example, in Japan Patent Laid Open Heisei 8-55908.

The side wall processing comprises the following steps: 1) A sacrificiallayer is formed on a layer to be processed; 2) The sacrificial layer ispatterned by lithography, for example. The sacrificial layer may beprocessed by slimming; 3) at or beside the side wall of the sacrificiallayer another sacrificial layer is formed as a mask; 4) using thissacrificial layer as a mask the layer to be processed is etched. By theside wall processing, it is possible to form a detailed pattern whichexceeds the resolution limits of lithography when the side wallprocessing is used.

However, in the side wall processing there are constraints to the shapeof a pattern which is formed by a sacrificial layer used as a mask. As aresult, the pattern which can be obtained by etching a layer to beprocessed includes unnecessary wiring patterns and short circuits aresometimes generated via these unnecessary wirings. In addition, when apattern density formed by a sacrificial layer which becomes a maskchanges significantly depending on the positions, the microloadingeffect sometimes occurs. This is because the speed of etching the layerto be processed changes depending on the positions. Also, the dishingeffect sometimes occurs during a CMP (Chemical Mechanical Polishing)process in a damascene process which is performed after the layer to beprocessed is etched. As a result, it becomes difficult to improve theyield.

BRIEF SUMMARY OF THE INVENTION

A method for manufacturing a semiconductor device according to oneembodiment of the present invention comprises: forming an insulationlayer to be processed over a substrate; forming a first sacrificiallayer in a first area over the substrate, the first sacrificial layerbeing patterned to form in the first area a functioning wiring connectedto an element; forming a second sacrificial layer in a second area overthe substrate, the second sacrificial layer being patterned to form inthe second area a dummy wiring; forming a third sacrificial layer at aside wall of the first sacrificial layer and forming a fourthsacrificial layer at a side wall of the second sacrificial layer, thethird sacrificial layer and the fourth sacrificial layer beingseparated; forming a concavity by etching the insulation layer to beprocessed using the third sacrificial layer and the fourth sacrificiallayer as a mask; and filling a conductive material in the concavity.

A method for manufacturing a semiconductor device according to oneembodiment of the present invention comprises: forming a conductinglayer to be processed over a substrate; forming a first sacrificiallayer in a first area over the substrate, the first sacrificial layerbeing patterned to form in the first area a functioning wiring connectedto an element arranged over the substrate; forming a second sacrificiallayer in a second area over the substrate, the second sacrificial layerbeing patterned to form in the second area a dummy wiring; forming athird sacrificial layer at a side wall of the first sacrificial layerand forming a fourth sacrificial layer at a side wall of the secondsacrificial layer, the fourth sacrificial layer being comprised of aplurality of connected components; forming a concavity by etching theconducting layer to be processed using the third sacrificial layer andthe fourth sacrificial layer as a mask; and filling an insulatingmaterial in the concavity.

A method for creating a layout of a semiconductor device according toone embodiment of the present invention comprises: deciding wiringpathways connecting a plurality of elements arranged within anintegrated circuit of the semiconductor device; synthesizing layout datafor creating a mask pattern for processing a insulating layer over asubstrate to realize the wirings based on the wiring pathways;calculating a change of density of the mask pattern based on the layoutdata; arranging a patter of a dummy wiring in the mask pattern to lessenthe change of density.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are exemplary planar views of a part of a substrate of asemiconductor device relating to one embodiment of the presentinvention.

FIGS. 2A-2C are diagrams which explain a functioning wiring and afunctioning area in a semiconductor device relating to one embodiment ofthe present invention.

FIG. 3 is an exemplary diagram for explaining a pattern density in afunctioning area and a dummy area.

FIGS. 4A-4F are diagrams which explain an outline of side wallprocessing.

FIGS. 5A-5F are diagrams which explain an outline of side wallprocessing.

FIGS. 6A-6F are diagrams which explain an outline of side wallprocessing.

FIGS. 7A-7D are diagrams which explain the occurrence of short circuitsdue to unnecessary wirings generated during side wall processing.

FIGS. 8A-8C are diagrams which explain the occurrence of short circuitsdue to unnecessary wirings generated during side wall processing.

FIGS. 9A-9D are diagrams which explain the occurrence of short circuitsdue to unnecessary wirings generated during side wall processing.

FIGS. 10A-10E are diagrams which explain a pattern in which shortcircuits do not occur easily even when unnecessary wirings are generateddue to side wall processing.

FIGS. 11A-11F are diagrams which explain a pattern in which shortcircuits do not occur easily even when unnecessary wirings are generateddue to side wall processing.

FIGS. 12A-12E are diagrams which explain a pattern in which shortcircuits do not occur easily even when unnecessary wirings are generateddue to side wall processing.

FIGS. 13A-13B are diagrams which explain a pattern in which shortcircuits do not occur easily even when unnecessary wirings are generateddue to side wall processing.

FIG. 14 is a functioning block structure diagram of a nonvolatilesemiconductor memory device related to one embodiment of the presentinvention.

FIGS. 15A-15C are diagrams which exemplary explain a stacked layerstructure of a memory block of a memory cell array in a nonvolatilesemiconductor memory device related to one embodiment of the presentinvention.

FIG. 16 is a diagram which shows functioning wirings of a memory cellarray and sense amplifier related to a nonvolatile semiconductor memorydevice related to one embodiment of the present invention.

FIG. 17 is a diagram which shows the addition of dummy wirings to afunctioning wiring of a memory cell array and sense amplifier related toa nonvolatile semiconductor memory device related to one embodiment ofthe present invention.

FIG. 18 is a diagram which shows microloading effects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, the preferred embodiments of the present invention are described.Furthermore, the present invention should not be interpreted as limitedto the embodiments described below. It is possible to work the presentinvention by various embodiments.

(First Embodiment)

FIG. 1 exemplarily shows a plane view of a part of a substrate of asemiconductor device related to one embodiment of the present invention.As is shown in FIG. 1 (A), the semiconductor device related to oneembodiment of the present invention includes, on the substrate, afunctioning area 101 and a region called a dummy area 102. A functioningarea is a region on a substrate in which a plurality of elementsrequired for exercising the functions of a semiconductor device (suchelements are hereinafter referred to as functioning elements) andwirings which connect the functioning elements (such wirings arehereinafter referred to as functioning wirings) are arranged. Afunctioning wiring and a functioning area can be inductively defined asfollows. First, an input/output terminal which inputs and/or outputssignals from and/or to exterior devices is a functioning element. And awiring which is connected to a functioning element is a functioningwiring. An element which is connected to a functioning wiring is afunctioning element. Furthermore, when a functioning element is aswitching element such as a transistor and this element is always in anOFF state, a wiring which is connected via this functioning element maybe further defined to be not a functioning wiring.

Further, a functioning area and a dummy area are not limited to belocated on the surface of the substrate but also located in the interiorof the substrate, above the surface of a layer which is arranged in aposition of a certain distance from the surface of the substrate. Thatis, a functioning area and a dummy area are formed in a single layer ora plurality of layers above, on, or beneath the substrate.

A dummy area is defined to be a region excluding functioning areas. Thatis, the region in which wirings which do not contribute to theoperations of circuits formed using the above stated functioningelements and functioning wirings, are arranged. In other words, a dummyarea is a region in which wirings not connected to functioning elementsand functioning wirings which is unrelated to the operations of thesemiconductor device, are arranged (such wirings are hereinafterreferred to as dummy wirings) or a region in which insulation materialis arranged between the functioning wirings and the dummy area.

FIG. 1 (B) and (C) exemplify a functioning area and a dummy area fromanother viewpoint. As is shown in FIG. 1 (B), the functioning area 103which is surrounded by the dummy area 104 does not have to be a convexshaped region but may also include a concave section. Also, there mayalso be a dummy area 105 within the functioning area 103. In addition,as is shown in FIG. 1 (C), there may be a plurality of functioning areas106 and 107 which is surrounded by a dummy area 108.

FIG. 2 is a diagram which explains the functioning wirings andfunctioning area from a number of viewpoints. In FIG. 2 (A), assumingthat the wiring of the reference number 201 connects together elementswhich are necessary for the functions of the semiconductor device, thefunctioning wiring 203 which is connected to the functioning wiring 201via a contact 202 is then shown as a functioning wiring. In addition,FIG. 2 (B) is a diagram which explains a functioning wiring from theviewpoint of a variation in a voltage which is applied. That is,following the point where operations of the semiconductor device begin,for example, after a certain period of time has elapsed since a powersupply, a wiring in which a variation in a voltage which is appliedexceeds a certain value, is a functioning wiring. The variation involtage is defined as the difference between the maximum voltage H andthe minimum voltage L after the point in time when operations begin. Forexample, the variation in voltage is required as the arithmeticdifference between H and L or as a ratio of the size of H to the size ofL (furthermore, when a ratio is calculated, a standard/base voltage isappropriately changed in the case where L becomes 0). In addition, inFIG. 2 (C), when the symbols 204 and 205 are referring to functioningwirings, an insulation region 206 (space between the functioning wirings204 and 205) which is located between these functioning wirings forms afunctioning area. Of course, the functioning wirings 204 and 205 whichform a functioning area is also shown.

In the description above, a functioning area is defined first and then aregion which is not a functioning area is defined as a dummy area.However, the definitions of the functioning area and dummy are notlimited to the definitions stated above. Reversely, a dummy area canalso be defined first. That is, a wiring which is not connected to acontact hole or even if a wiring is connected to a contact hole, a dummywiring is defined as a wiring with a fixed voltage which is applied atoperation time of a semiconductor device or a wiring with a voltagevariation within a predetermined level. Then, a dummy area can bedefined as a region which includes a dummy wiring and insulationmaterial which is in contact with a dummy wiring, and a functioning areacan be defined as a region excluding a dummy area.

In semiconductor devices, particularly in semiconductor memory deviceswhich include memory circuits, the same pattern of a detailed structurefor achieving small size repeatedly appears in a functioning area.However, because a dummy area is not related to a functioning of thesemiconductor device, in a dummy area either there are no wirings at allor there are few wirings compared to a functioning area. Therefore, whenthe number of wirings which are crossed by a line segment of a certainlength (such number is generally defined as an inverse of a pitch) orthe ratio of area occupied by elements and wirings in a certain area(such ration is generally defined as a patter density) is calculated,generally the inverse of a pitch or the pattern density in a dummy areabecomes smaller than the inverse of a pitch or the pattern density in afunctioning area.

Therefore, a graph of a change in a pattern density to a position on asubstrate is drawn as in FIG. 3, for example. That is, the patterndensity is different between the dummy area and the functioning area.The pattern density of the functioning area is larger than the patterndensity in the dummy area. Also, as in a memory cell array of anonvolatile semiconductor memory device, when the same pattern isregularly and repeatedly arranged, a periodically changing graph of achange in a pattern density in the interior of a functioning area isobtained. In addition, when a functioning area and a dummy area areregularly and repeatedly arranged, a periodically changing graph of theposition in which this type of functioning area and dummy area arearranged is obtained.

In addition, a spatial frequency of a pattern can be calculated for eachposition on a substrate. For example, (1) an image of a pattern, whichis formed by wirings and insulation spaces formed in/on a substrate, isdecomposed into square pixels having a side length of a half of aminimum process dimension according to Shannon's Theorem for example,(2) the adjacent pixels are grouped into square blocks of pixels, (3)the discrete Fourier transformation or discrete cosine transformation isapplied to each groups.

As to the spatial frequency as calculated above, when the same patternof a functioning area and a dummy area is regularly and repeatedlyarranged, the spatial frequency regularly changes. In addition, when thesame pattern is repeated in the interior of a functioning area thespatial frequency periodically changes spatially.

The value of the inverse of a pitch is sometimes different depending onthe direction of a line segment of certain length for calculating anumber of wirings crossing a line of a length of a predetermined length,and there is a problem in calculating mechanically and accurately thepitch. While by calculating a patter density, a problem such as incalculating a pitch does not occur because a pattern density iscalculated as a value of one dimension for a region of a certain area,there is a problem in which it is difficult to know the direction ofwirings for example. This problem is overcome by calculating a spatialfrequency because a spatial frequency can be calculated mechanically asa two dimensional value to a block which expands in two dimensions.

When a pattern density or a spatial frequency in a functioning area anddummy area are significantly changes, the possibility of dishing effectsduring a planarization process such as CMP or the possibility ofmicroloading effects due to a difference in etching speed within asubstrate becomes greater.

FIG. 18 explains the occurrence of microloading effects. In FIG. 18, amask is arranged in the white sections and the state after ananisotropic etching in a perpendicular direction of the diagram to theblack parts. Even if an anisotropic etching is performed in aperpendicular direction, it is inevitable that an etching in horizontaldirection is slightly performed. As a result, even if a mask of the samewidth is arranged on the white sections, when a pattern density of amask pattern or a spatial frequency is different depending on positionson the substrate, the speed of etching in a horizontal direction isdifferent. FIG. 18 shows a result where the speed of etching in ahorizontal direction is different. Specifically, when a pattern densityor a spatial frequency is in a high position, the speed of etching in ahorizontal direction becomes greater compared to a low position. As aresult, the higher the position of a pattern density or a spatialfrequency is, the larger the amount of erosion of the part beneath amask and the width of the white part becomes smaller. In FIG. 18,because the pattern density or the spatial frequency in an end part fromthe central part is high, the width of the white part of the end partbecomes smaller.

Of course, depending on the etching conditions, mask material, ormaterial to be etched, it is sometimes the case that the lower thepattern density or spatial frequency is, the larger the speed ofetching.

When microloading effects or dishing effects occur, the manufacturingyield of semiconductor devices decreases. Thus a semiconductor devicerelated to one embodiment of the present invention is manufactured sothat changes in a pattern density and/or a spatial frequency under sidewall processing, which accompany the restrictions in pattern formation,become smaller or equal. While in addition, the occurrence of shortcircuits becomes greater under side wall processing because unnecessarywirings are generated, in the manufacturing method of a semiconductordevice related to one embodiment of the present invention, this problemis solved.

Below, an outline of a side wall processing is explained while referringto FIG. 4 to FIG. 6. Next, the phenomenon whereby short circuits occureasily when the changes in pattern density or spatial frequency in aside wall processing are made smaller is explained while referring toFIG. 7 and FIG. 8.

FIG. 4 (A) shows a cross section of a substrate and a structure which isformed on the substrate. A layer 402 to be processed is deposited on asubstrate 401, a first sacrificial layer 403 is further deposited on thelayer 402 to be processed and the first sacrificial layer 403 is formedinto a certain pattern by lithography. FIG. 4 (B) shows a planar view ofthe substrate 401.

Furthermore, there are cases where the layer to be processed is aconductive layer having conductive properties and where an insulationlayer having insulation properties. Polysilicon, for example, may beused as a material for a conductive layer and silicon oxide may be usedas a material for an insulation layer.

FIG. 4 (C) and (D) show a structure after a slimming process has beenperformed on the first sacrificial layer 403 to make a finer pattern ofthe first sacrificial layer 403. Furthermore, slimming is not anessential process and can be performed according to necessity.

Next, the material of the second sacrificial layer 404 has beendeposited on the layer 402 to be processed on which the pattern by thefirst sacrificial layer 403 is formed. FIG. 4 (E) and (F) show astructure after anisotropic etching has been performed so that a secondsacrificial layer 404 is left at or beside the side wall of the firstsacrificial layer 403. Because the second sacrificial layer 404 isformed at or beside the side wall of the first sacrificial layer 403,the shape of the second sacrificial layer 404 becomes a loop shape as isshown in FIG. 4 (F). The second sacrificial layer surrounds the patternformed by the first sacrificial layer 403.

FIG. 5 (A) and (B) show a structure after the first sacrificial layer403 has been selectively removed. Then, FIG. 5 (C) and (D) show astructure when the layer 402 to be processed is etched using the secondsacrificial layer 404 as a mask. A concavity is formed in the layer 402except under the second sacrificial layer 404. After this the secondsacrificial layer 404 is selectively removed and the structure shown inFIG. 5 (E) and (F) are obtained.

As stated above, because the second sacrificial layer 404 has a loopshape the concavity pattern formed by the etching layer 404 using thesecond sacrificial layer 404 as a mask also has a loop structure.Therefore, a part of the loop structure generally is removed in order toform one or more wirings. In addition, there are cases when there is aneed for a process to restrict the range in which a different materialis filled between the second sacrificial layer 404, which is left byetching. Then, as is shown in FIG. 6 (A) and (B), for example, in orderto restrict the range in which a different material is filled afterobtaining the structure in which a part of the layer 402 to be processedis removed, another material 405 is filled as in shown in FIG. 6 (C) and(D), for example. Furthermore, another material 405 can be the samematerial as the layer 402 to be processed. That is, another material 405may be a different material to the material which is filled in theconcavity formed between the layer 402 to be processed.

Then, another material 406 is filled between the layers 402 to beprocessed as shown in FIG. 6 (E) and (F). That is, a structure in whichthe material 406 is sectioned by the layer 402 to be processed can beobtained. A width which is sectioned by the material 404, that is, thewidth of a line of a pattern formed on the layer 402 to be processed canbe made smaller than the resolution limits of lithography by side wallprocessing. In addition, when slimming is performed on the firstsacrificial layer 403, the width of the material 406, that is, thedistance between the layers 402 to be processed 402, can be made smallerthan the resolution limits of lithography.

Furthermore, the process for removing a part of a loop, the process forfurther depositing another material 405 and the process for depositingyet another material 406 can be appropriately interchanged. For example,the material 406 may be deposited in the structure in FIG. 5 (E) and (F)and then a region in which another material 406 is deposited in FIG. 6(C) and (D) is etched and a part of the loop is removed.

FIG. 7 (A) shows a functioning area 1 and a functioning area 2 on thesubstrate with a dummy area 1 which exists between these functioningareas. Furthermore, the functioning area 1 and the functioning area 2may be a part of the same functioning area.

In FIG. 7 (A), because there are no wirings in the dummy area 1 thepattern density and/or the spatial frequency in the functioning area 1and functioning area 2 and the pattern density and/or the spatialfrequency in the dummy area 1 are significantly different. As a result,microloading effects and/or dishing effects occur as stated above.

Thus, the conducting material which becomes a wiring 701 is deposited onthe substrate in the shape of a layer, the second sacrificial layer 702is added to the functioning area 1 and functioning area 2 and alsoformed on the dummy area 1 and etched as is shown in FIG. 7 (B) makingthe differences of spatial frequency etc. smaller.

Because of the constraints due to side wall processing, as is shown in

FIG. 7 (B) the number of dummy wirings that are formed on the dummy area1 becomes an even number. In addition, when the second sacrificial layeris extended only in one direction, the force received in the verticaldirection makes it easy for the shape of the second sacrificial layer tobreak up. As a result, a decrease in yield occurs due to the formationof unnecessary wirings in the dummy area 1. Thus, utilizing the factthat the number of dummy wirings is an even number, adjacent secondsacrificial layers which are formed in the dummy area 1 are connected ina ladder shape and the structure shown as a planar view in FIG. 7 (C) isobtained.

However, in the structure shown in FIG. 7 (C), when dust 703 and dust704 which have conductive properties are attached as shown in FIG. 7(D), a wiring in the functioning area 1 and another wiring in thefunctioning area 2 short out.

A method for detecting whether this type of short circuit occurs isconsidered. For this consideration, a region which becomes equipotentialby a wiring is described as a node. In addition, in order to distinguishbetween a wiring within a functioning area and a wiring within a dummyarea, a node which describes a wiring in a functioning area is forexample colored black and a node which describes a wiring in a dummyarea is colored white. In addition, an insulation space between twowirings can be described as an edge which connects a node whichdescribes these two wirings. Then, a graph structure can be obtainedwhich corresponds to a wiring pattern. The graph shown in this graphstructure is hereinafter called a pattern graph.

A pattern graph corresponding to the pattern shown in FIG. 7 (C) isshown in FIG. 8 (A). The subgraph on the left of the node 801 is apattern graph corresponding to the functioning area 1, the subgraph onthe right of the node 803 is a pattern graph corresponding to thefunctioning area 2 and the subgraph constructed by the node 802 and theedges connected to the node 802 is a pattern graph corresponding to thedummy area 1.

First, assuming that the dust 703 is attached, the rightmost wiring inthe functioning area 1 and the wiring in the dummy area 1 get connectedelectrically. This situation is equivalent to a fusing together of thenode 804 and the node 803 in the pattern graph and a new node 804 isproduced as is shown in FIG. 8 (B).

Next, assuming that the dust 704 is attached, the wiring in the dummyarea 1 and the leftmost wiring in the functioning area 2 get connectedelectrically. In this situation, the node 804 and the node 803 fusetogether in the pattern graph and a new node 805 is produced as shown inFIG. 8 (C). Then, the dummy area 1 disappears from the pattern graph.

Even if the dust 704 is attached before the dust 703, similarly thepattern graph shown in FIG. 8 (C) is obtained.

Therefore, in the case where different black nodes F1 and F2 areconnected via two edges to a white node D, D and F1 fuse together, andwhen the fused node and F2 fuse together the dummy area equivalent to Ddisappears and a short circuit occurs in the functioning areacorresponding to F1 and F2.

Therefore, in the pattern graph, when a plurality of edges are connectedto a white node, if a pattern is formed so that the number of edgesamong the plurality of edges which are connected to a black node is atmost one, a short circuit occurring via a wiring of a dummy areacorresponding to this white node can be suppressed.

That is, the shape of the second sacrificial layer which is formed in adummy area does not become one geometrically connected component and maybe comprised of a plurality of connected components. This is because ifthe shape of the second sacrificial layer which is formed in a dummyarea becomes one connected component, because the shape of a conductingmaterial in the dummy area is expressed as one connected component, thatis, one white node, two black nodes are connected to this node and whenthe fusing together of nodes stated above occurs twice, the subgraph ofthe dummy area disappears.

FIG. 9, unlike FIG. 7, is a diagram which explains the dangers of ashort occurring due to dust being attached during a process to obtain awiring pattern by making an insulation layer into a layer to beprocessed, forming the second sacrificial layer on the insulation layerand performing damascene processing. As is shown in FIG. 9 (A), it isassumed that the dummy area 2 exists between the functioning area 3 andthe functioning area 4. In order to arrange wirings in the functioningarea 3 and the functioning area 4, a plurality of second sacrificiallayers 902 is formed above the insulation layer 901 within thefunctioning area 3 and the functioning area 4 and it is sufficient toform a second sacrificial layer 902 in the periphery of the dummy area2.

Then, the insulation layer 901 is etched using the second sacrificiallayer 902 as a mask and as is shown in FIG. 9 (B), the secondsacrificial layer 902 is selectively etched and as is shown in FIG. 9(C), and a conducting material 903 is filled into the insulation film901 by a damascene process.

However, in this state, a large difference of the spatial frequency ofpattern and/or the density of pattern is produced between thefunctioning areas 3 and 4 and the dummy area 2. Therefore, as is shownin the upper surface diagram in FIG. 9 (D), a space 904 is arrangedwithin the dummy area 2 and the difference in the spatial frequencybecomes smaller or disappears. Even in this case, a pattern is arrangedso that a pair of the spaces 904 is created. However, when a patterngraph is created for the pattern shown in FIG. 9 (D), the pattern graphbecomes the same as the pattern graph shown in FIG. 8 and the fact thatit becomes easier for short circuits to occur is detected.

FIG. 10 (A) and (B) exemplify a resolution method for also arrangingwithin the dummy area 2 a space which extends parallel up and down tothe space arranged in the functioning areas 3 and 4. Even in this case,due to the constraints due to the side wall processing, the secondsacrificial layer 1002 for arranging an even number of spaces isarranged above the insulation layer 1001 within the dummy area 2. Then,etching is performed using the second sacrificial layer 1002 as a mask,the second sacrificial layer 1001 is selectively removed and aconducting material 1003 is filled using a damascene process and awiring is formed. The graph pattern shown in FIG. 10 (E) is a graphpattern created for the pattern shown in FIG. 10 (D). All of the whitenodes are edges connected to a node and the number of edges connected toa black node is at most one.

Generalizing the case of FIG. 10 (E), when a second sacrificial layerformed at or beside a side wall of a first sacrificial layer formed in afunctioning area, and a second sacrificial layer formed at or beside aside wall of a first sacrificial layer formed in a dummy area, areformed, it is sufficient that they are formed so that they becomeseparated from each other. When the maximum width of a secondsacrificial layer is d, it is sufficient if the distance between thefirst sacrificial layer formed in a functioning area and a firstsacrificial layer formed in a dummy area is twice larger than d.

FIG. 11 and FIG. 12 are diagrams which explain a different patternformation in a dummy area when an insulation layer is the layer to beprocessed. As is shown in FIG. 11 (A) and (B), a first sacrificial layer1102 is formed above an insulation layer 1101. While in the crosssectional diagram in FIG. 11 (A) one first sacrificial layer 1102appears to be arranged in the dummy area, according to the upper surfacediagram shown in FIG. 11 (B), a first sacrificial layer is arranged in azig zag shape in the dummy area. That is, the shape of a firstsacrificial layer in the dummy area is a shape which consists of aplurality of connected elements. Then, as is shown in FIG. 11 (C) and(D), slimming is performed on the first sacrificial layer 1102. Then, asis shown in FIG. 11 (E) and (F), a second sacrificial layer 1103 isformed on the side wall of the first sacrificial layer 1102.Furthermore, as is shown in FIG. 11 (F), arrangement and slimming of thefirst sacrificial layer is performed so that the second sacrificiallayer which are formed on the side walls of the upper and lower firstsacrificial layers are connected in the dummy area.

Then, the first sacrificial layer is selectively removed and etching isperformed by etching the insulation layer 1101 to a certain depth usingthe second sacrificial layer as a mask and the structure shown in FIG.12 (A) and (B) is obtained. That is, a torus shape having a plurality ofholes appears in the dummy area. The second sacrificial layer isselectively removed, a conductive material is filled by a damasceneprocessing and the structure shown in FIG. 12 (C) and (D) is obtained.The graph shown in FIG. 12 (E) is a graph created for this structure.All of the white nodes are edges connected to a node and the number ofedges connected to a black node is at most one.

By arranging a torus shape in a dummy area, even if a force is appliedfrom the side of the torus shape, it is difficult to break up the shapeand it becomes possible to prevent the generation of defects due to abreak up of a pattern in the dummy area.

FIG. 13 (A) and (B) show other examples of a pattern created in a dummyarea. FIG. 13 (A) and (B) show, other than a torus, shape pattern whichare difficult to break up. FIG. 13 (A) shows a pattern arranged in apolygonal shape such as a parallelogram or a rhombus shape. In addition,in FIG. 13 (B) a pattern based on a circular shape is created in thedummy area. When a graph is made for any of the patterns, all of thewhite nodes are edges connected to a node and the number of edgesconnected to a black node is at most one, and the fact that this is apattern in which short circuits are not generated easily is detected.

Furthermore, in the creation of a layout of a semiconductor device,first its hardware is described with a level of abstraction called anRTL (Register Transfer Level) using a hardware description language forexample, based on the specification data of a semiconductor integratedcircuit. Next, this description is logically synthesized using a logicalsynthesis tool and as a result, is developed to a level of abstractioncalled a gate level. That is, as a logical synthesis result it ispossible to obtain data of a logic circuit diagram. Then, it is alsopossible to produce a net list from the data of this logic circuitdiagram.

Next, a plurality of elements are arranged on an integrated circuitbased on the data of this logic circuit diagram and by deciding thewiring pathways between this plurality of elements layout data iscreated for creating a mask. That is, the arrangement of wirings and afunctioning area is decided. Then, a distribution of a spatial frequencyof a pattern from this layout data is demanded.

That is, in a device for creating a layout of a semiconductor device,the distribution of the spatial frequency of a patter is investigatedand a detection is performed to check whether there are places in whichchanges in the spatial frequency exceed a predetermined change amount.If, it is detected that a change in the spatial frequency exceeds apredetermined change amount, a warning is produced for the occurrence ofmicroloading effects and an error message is displayed etc. In addition,if a place exists in which a spatial frequency is low, a warning isproduced for the occurrence of dishing effects, the places in whichdesign of a dummy wiring should be performed is indicated to a designerand design of the dummy wiring is automatically performed etc.

After this, a pattern graph is created, and a check is performed as towhether the conditions have been met for the number of edges connectedwith a node (black node) corresponding to a functioning area wiring isat most one or not, these edges being connected to a node (white node)corresponding to a dummy area wiring. If is detected that theseconditions have not been met, redesign is encouraged or a design ofdummy wirings is automatically performed.

In addition, because the pattern of the second sacrificial layer extendsin one direction, by calculating a distribution of a pattern spatialfrequency, it is possible to detect whether a pattern breaks up easilywhen a force is applied from the side. When a pattern extends in onedirection, the direction in which the pattern extends becomes a spatialfrequency value close to 0 and a perpendicular direction to thisdirection becomes a value larger than 0. Thus, a pattern of asemiconductor process is separated into a pattern of a functioning areaand a pattern of a dummy area, a spatial frequency of a dummy areapattern is calculated, and by checking whether a value of a spatialfrequency in one direction which is close to 0 is serially connected ornot, it becomes possible to detect whether a pattern of the secondsacrifice film connected to a dummy area breaks up easily or whether theyield of a semiconductor device is reduced.

Furthermore, as a characteristic of side wall processing a dummy wiringmay easily occur in a region in which pattern periodicity of a wiring orinsulation space in an integrated circuit changes. Thus, a layoutpattern is analyzed and instead of distinguishing between a functioningarea and dummy area, a distribution of a pattern spatial frequency iscalculated and the detection is performed in a region in which a spatialfrequency value exceeds a predetermined change amount. Then, based onthis detection, it becomes possible to separate the dummy area and thefunctioning area. Based on the separation result, the dummy area patternand the functioning area pattern are separated into different layoutsfor example. Then, the functioning area pattern which has been separatedby this type of procedure may be verified by a design rule check. Thatis, the functioning area pattern is checked as to whether it conforms togeometric design rules which are designed while paying attention to eachtype of obtained restriction once the manufacturing process has beenverified.

Generally, when a wiring pattern is separated between a functioning areaand a dummy area based on the connection relationship of a wiring, alarge amount of calculation is required which makes the wiring becomesvery complex. However, calculation of the amount of change in spatialfrequency may require a calculation amount unrelated to the complexityof the wiring. As a result, it is possible to perform separation of afunctioning area and a dummy area in a short period of time and becausea design rule check is not performed on the dummy area it is possible toremove the occurrence of simulated errors caused by dummy area wiringswhich has been indicated as a conventional problem. As a result, it isalso possible to complete the design of a semiconductor device in ashort period of time.

(Second Embodiment)

As an embodiment of the present invention, a nonvolatile semiconductormemory device which uses a NAND flash memory as a semiconductor deviceof one embodiment of the present invention is described below.

FIG. 14 shows a block diagram of a nonvolatile semiconductor memorydevice related to an embodiment of the present invention. Thenonvolatile semiconductor memory device 1 shown in FIG. 14 is arrangedwith an I/O control circuit 12, a logic control circuit 13, a statusregister 14, an address register 15, a command register 16, a controlcircuit 17, a voltage generation circuit 18, a row decoder 19, a rowaddress buffer 20, a memory cell array 21, a sense amplifier 22, a dataregister 22, a column decoder 24 and a column buffer 25.

The I/O controller circuit 12 sends and receives data between externalinput/output terminals I/O 1 to I/O 16 and the data register 23 whenreading data or when programming data. In addition, the I/O controllercircuit 12 outputs address data which is input from the externalinput/output terminals I/O 1 to I/O 16 to the address register 15 whenreading data or when programming data. Also, the I/O controller circuit12 outputs commands supplied from the external input/output terminalsI/O 1 to I/O 16 to the command register 16. In addition, the I/Ocontroller circuit 12 outputs status data (data for informing anexternal device on the various states within the chip) which is inputfrom the status register 14 to an external device via the externalinput/output terminals I/O 1 to I/O 16. While in FIG. 14 the externalinput/output terminals are expressed as I/O 1 to I/O 16 so that thenumber of external input/output terminals is 16, an arbitrary number ofexternal input/output terminals may be used.

The logic control circuit 13 outputs external control signals such as achip enable signal CE, a write enable signal WE, a read enable signalRE, an address latch enable signal ALE, a command latch enable signalCLE and a write protect signal WP which are externally input to thecontrol circuit 17.

The status register 14 is a register for informing an external device onthe various statuses of the chip and includes a ready/busy registerwhich holds data which shows whether the chip is in a ready or busystatus, a programming status register which holds data which shows aprogramming pass or fail, a programming error register which holds datawhich shows the existence of a program error status (program verifypass/fail) and an overwrite status register which holds data which showsthe existence of an overwrite status (overwrite verify pass or fail).

The address register 15 decodes address data input from the I/O controlcircuit 12, outputs a row address to the row address buffer 20 andoutputs a column address to the column address buffer 25.

The command register 16 outputs a command which is input from the I/Ocontrol circuit 12 to the control circuit 17.

The control circuit 17 outputs a command which is input from the commandregister 16 to the voltage generation circuit 18. In addition, thecontrol circuit 17 performs a data program, data read and data erasecontrol sequence of controls based on an external control signal inputfrom the logic control circuit 13 and a command input from the commandregister 16 according to an operation mode.

The voltage generation circuit 18 is a circuit for generating variousVpp voltages (program voltage Vpgm, verify voltage Vr, program passvoltage Vpass, read voltage Vread, etc.). This voltage generationcircuit 18 is controlled by the control circuit 17.

The row decoder 19 includes a word line drive circuit which selects aword line of the memory cell array 21 and drives a word line based on arow address (page address) stored in the row address buffer 20.

The row address buffer 20 stores a row address input from the addressregister 15.

The memory cell array 21 comprises a plurality of NAND cell units. EachNAND cell unit is comprised by a memory string in which a plurality ofelectrically reprogrammable nonvolatile memory cells are seriallyconnected, and a memory block which includes a plurality of NAND cellunits, each NAND cell unit being connected to a selection transistor ateach end. The memory cell array 21 is generally comprised by a pluralityof memory blocks. A word line connects the control gates of nonvolatilememory cells of every NAND cell unit in a memory block. The selectiongates of selection transistors are connected to a section gate linewhich is arranged parallel to word lines. A group of NAND cell unitswhich share a word line comprise a memory block which is a unit of dataerasure. A plurality of these memory cell blocks is included within thememory cell array 21.

When reading data the sense amplifier 22 reads data which is stored in anonvolatile memory cell selected by the row decoder 19 and the columndecoder 24 and outputs to the data register 23.

The data register 23 is connected with the I/O control circuit 12 viathe I/O bus 26. When reading data the data register 23 outputs data readvia the sense amplifier circuit 22 to the input/output terminals I/O 1to I/O 16 via the I/O control circuit 12. In addition, when programmingdata the data register 23 outputs via the input/output terminals I/O 1to I/O 16 and the I/O control circuit 12 data to be programmed, which isloaded from an external controller 2, to the sense amplifier circuit 22.Furthermore, the data register 23 may include a trimming data register(not shown in the diagram) for storing trimming data (voltage levelsetting data for operation voltage adjustment or clock data for clockadjustment within a memory chip) which is used when demanding/requestinga parameter which controls an operation of the memory cell array 21, anda defective block address register (not shown in the diagram) whichstores address data of a defective block detected as result of the abovestated test operation.

The column decoder 24 selects a bit line of the memory cell array 21based on a column address stored in the column buffer 25. The columnbuffer 25 stores a column address which is input from the addressregister 15. The I/O bus 26 is a bus which connects the I/O controlcircuit 12 with the data register 23.

FIG. 15 is a diagram which exemplarily explains a layered structure of amemory block in the memory cell array 21. An insulation layer such as anoxide layer is formed on the surface of a substrate and wirings whichform the select lines 1501, 1503 and word lines 1502-1, 1502-2, . . . ,1502-m, formed above the substrate, are arranged above this as shown inFIG. 15 (A). These select gate lines and word lines are connected to therow decoder 19. Furthermore, an active region which extends in adirection perpendicular to the select gate lines and word lines isformed on the substrate using, for example, an STI (Shallow TrenchIsolation) structure. The select gate lines are also functioning as gateelectrodes of the selection transistors which are formed in this activeregion. In addition, if a nonvolatile memory cell is a memorytransistor, a charge storage layer is formed between the active regionand a word line.

A common source line 1504 is arranged on a layer above the layer inwhich a select gate line and a word line are arranged via an interlayerinsulation material. Then, again via an interlayer insulation material,the bit lines 1505-1, 1505-2, and 1505-n are arranged. Lines 1506-1,1506-2, and 1506-k which connect the sense amplifier 22 with a selectorcircuit 27 are arranged on the same layer as the layer in which the bitlines is arranged. The selector circuit 27 is a circuit for selecting abit lit which is connected to a sense amplifier when the number of senseamplifiers of the sense amplifier circuit and the number of bit linesare different (generally the number of sense amplifiers is not largerthan the number of bit lines).

FIG. 15 (B) shows a cross sectional view of a cross section along theline A-A in FIG. 15 (A). The wiring 1506 is connected with the selectorcircuit 27 via a contact, and the bit line 1505 is also connected withthe selector circuit 27 via a different contact.

FIG. 15 (C) shows a cross sectional view of a cross section along theline AA-AA in FIG. 15 (B). In FIG. 15 (C) the lines 1506-1, 1506-2, and1506-3 which connect the sense amplifier circuit 22 and the selectorcircuit 27 are lined on the left side and the bit lines 1505-1, 1505-2,and 1505-3 are lines on the right side.

FIG. 16 is a diagram which shows the structure shown in FIG. 15 (C) inmore detail. That is, FIG. 16 shows wirings in a functioning area of alayer in which the cross section AA-AA in FIG. 15 (B) is drawn. A largenumber of bit lines of the memory cell array 21 are lined in the columnlabeled 1601 and a large number of wirings which connect the senseamplifier circuit 22 with the selector circuit 27 are lined in thecolumn labeled 1602. The part labeled 1603 is a region between thecolumn labeled 1601 and the column labeled 1602 and the selector circuit27 is arranged on a layer above this region.

A part in which bit lines are lined consecutively similar to the partlabeled 1604 and a part in which bit lines are not lined similar to thepart 1605, are lined alternately in the column labeled 1601. The partlabeled 1605 is a region in which nonvolatile memory cells are notarranged and is called a shunt region of the memory cell array 21.

In addition, a part exists in which bit lines are lined consecutivelysimilar to the part labeled 1606 and another part exists in which bitlines are not lined similar to the part 1607 and 1608, in the columnlabeled 1602. The part labeled 1608 corresponds to the shunt region ofthe memory cell array 21. Because there are no bit lines in the shuntregion of the memory cell array 21, it is not necessary to arrangedsense amplifiers in lines and there are no wirings. In addition, thepart labeled 1606 corresponds to one group of sense amplifiers which arearranged in the sense amplifier circuit 22. Also, in the case where onesense amplifier is responsible for amplification of voltages of aplurality of bit lines, a bit line and a sense amplifier no longercorrespond as one pair. As a result, a region where there are no wiringsas in the part labeled 1607, periodically appears. As is shown in FIG.16, generally, the width of the region labeled 1607 becomes smaller thanthe width of the region labeled 1608 which is a region which correspondsto the shunt region of the memory cell array 21. This is because aregion exists which corresponds to the region labeled 1607, on both endsof the region labeled 1608.

In addition, when the pitch of bit lines arranged in the column labeled1601 is pbl, that is, when the width of a bit line and the width of aspace between bit lines is pbl as shown in FIG. 16, and when the pitchof bit lines arranged in the column labeled 1602 is pb1i, generally, therelationship 2×pbl>=pbli>=pbl holds. This is because it is difficult tosignificantly change the width of the second sacrificial layer by sidewall processing.

It is possible to create a graph of a position in a substrate and apattern density as is shown in FIG. 3 for the wiring shown in FIG. 16. Apart with a high pattern density 1604 corresponding to pbl and a partwith a low pattern density 1605 which corresponds to the shunt region inthe memory cell array 21, appears alternately in the column labeled1601. Therefore, if a dummy wiring is not created in the shunt region ofthe memory cell array 21, a difference occurs in the pattern density.

In addition, a part with a high pattern density 1606 corresponding topbli and a part with a low pattern density 1605 which corresponds to theregions labeled 1606 and 1607, appear alternately in the column labeled1602. Therefore, if a dummy wiring is not created in the regions labeled1607 and 1608, a difference occurs in pattern density, spatialfrequency, etc.

Therefore, as is shown in FIG. 17, in order to reduce this difference inpattern density, in spatial frequency, etc., the regions labeled 1605,1606, 1607 and 1608 are treated as dummy areas and a dummy wiring isarranged. As stated above, because a region 1701 which corresponds tothe region labeled 1607 exists on both ends of the region labeled 1608,a dummy wiring of the region labeled 1607 is formed. In addition, if apattern does not exist in the region labeled 1703, because patterndiffers significantly, a dummy pattern is formed.

By creating a dummy pattern in this way it is possible to reduce changesin pattern density and prevent an occurrence of the effects ofmicroloading and dishing. In addition, by using side wall processing itis possible to form a pattern which exceeds resolution limits andrealize a small scale semiconductor device. When side wall processing isused, unnecessary wiring were conventionally created and short circuitseasily occurred via these unnecessary wirings, however, by applying anembodiment of the present invention it is possible to prevent theoccurrence of these short circuits.

According to an embodiment of the present invention it is possible toprevent the occurrence of shorts circuits due to unnecessary wiringsformed by side wall processing and also prevent the occurrence ofmicroloading and dishing effects. It is also possible to realize animprovement in yield while achieving a small scale semiconductor device.

What is claimed is:
 1. A semiconductor device comprising: a first lineextending in a first direction; a second line extending in the firstdirection; a dummy area provided between the first line and the secondline, the dummy area including first to fifth electrically isolatedconductors, the first to third electrically isolated conductors beingarranged in a second direction which is neither parallel nor orthogonalto the first direction, the dummy area including the second, fourth, andfifth electrically isolated conductors being arranged in a directionwhich is different from the second direction, the first to fifthelectrically isolated conductors being surrounded by only firstinsulating lines and second insulating lines, the first insulating linesextending in the second direction, the second insulating lines crossingthe second direction.